Cisco Catalyst 4948 User Manual

Chapter 13
Quality of Service
See the following sections to configure and use these features:
■ 13-1: QoS Theory: Discusses the various operations and mechanisms that make up
quality of service (QoS) as a whole
■ 13-2: QoS Configuration: Explains the sequence of steps necessary to configure
and monitor QoS on a Catalyst switch
■ 13-3: QoS Data Export: Presents the configuration steps needed to gather and send
QoS statistics information to external collection devices
13-1: QoS Theory
■ QoS defines policies on how switches and routers deliver different types of traffic. A
QoS domain is the entire collection of network devices that are administered so that
they adhere to the QoS policies.
■ To guarantee that QoS policies are met, QoS must be configured on all switches and
routers end-to-end across the network.
■ Traffic should be classified at the edges of the QoS domain. Where this isn’t possi-
ble, classify traffic as close as possible to the source. Classification can occur at
Layer 2 or Layer 3, depending on the network functions available at the edge.
■ The top portion of Figure 13-1 shows QoS operations on a Catalyst switch, includ-
ing the following:
■ Classification: Selects specific traffic to which a QoS policy can be applied. The
priority values of inbound frames can also be trusted or reclassified.
■ Policing: Limits the bandwidth used by a traffic flow. Policers can control aggre-
gate or individual flows and can also mark or drop traffic.

Cisco Catalyst 4948 Specifications

General

Switching Capacity	136 Gbps
Forwarding Rate	102 Mpps
Rack Units	1U
MAC Address Table Size	32, 000 entries
Authentication Method	RADIUS, TACACS+
RAM	256 MB
Flash Memory	64 MB
Power Device	Internal power supply
Voltage Required	100-240 VAC
Weight	16.5 lbs
Operating Humidity	10% to 85% non-condensing
Ports	48 x 10/100/1000
Power Supply	Internal
Layer Support	Layer 3
Jumbo Frame Support	Yes (up to 9216 bytes)
Routing Protocol	RIP, OSPF, EIGRP, BGP
Remote Management Protocol	SNMP, Telnet, SSH
Features	VLAN support, QoS
Compliant Standards	IEEE 802.3, IEEE 802.3u, IEEE 802.3ab, IEEE 802.1Q, IEEE 802.1p
Operating Temperature	32 °F to 104 °F (0 °C to 40 °C)